Effect of subsurface negative segregation induced by M-EMS on componential homogeneity for bloom continuous casting

The subsurface negative segregation behavior and its effect on componential homogeneity of as-cast bloom within a section size of 320 mm x 425 mm under different stirrer currents were investigated with the aid of numerical simulation. To this end, plant trials were conducted based on a curved bloom caster in Shaoguan steel. The results show that the minimum subsurface negative segregation degree is decreased from 0.977 to 0.858 and its corresponding location moves from 16 mm to 11.9 mm distance from strand surface as the stirrer current is increased from 100 A to 600 A. The carbon content fluctuation range of rolled product cross-section first reduces and then increases because of the integrated effects of two factors: melt temperature at the mold exit center decreases (that is, undercooling is increased), whereas the local segregation degree increases with the increase in the stirrer current. As compared to the normal M-EMS parameters (600 A/2.5 Hz), the fluctuation range of carbon content at the cross-section of rolled product is reduced from 0.038 to 0.012 wt.% under the optimized M-EMS parameters of 200 A/2.5 Hz.